The invention is generally related to the field of forming copper interconnects in semiconductor devices and more specifically to a post-copper CMP clean process.
As integrated circuits become more and more dense, the width of interconnect layers that connect transistors and other devices of the integrated circuit to each other is reduced. As the width decreases, the resistance increases. Accordingly, many companies are looking to switch from a traditional aluminum interconnect to a copper interconnect. Unfortunately, copper is very difficult to etch in a semiconductor process flow. Therefore, damascene processes have been proposed to form copper interconnects.
A typical damascene process consists of forming an interlevel dielectric 12 first over a semiconductor body 10, as shown in FIG. 1A. The interlevel dielectric 12 is then patterned and etched to remove the dielectric material from the areas 14 where the interconnect lines are desired, as shown in FIG. 1B. In a dual damascene process, via holes are also formed at this time. Referring to FIG. 1C, a barrier layer 16 is then deposited over the structure including over the dielectric 12 and in the areas 14 where the dielectric has been removed. A copper seed layer 18 is then formed over the barrier layer 16. The copper layer 20 is then formed from the seed layer 18 using, for example, an electroplating process, as shown in FIG. 1D. Chemical-mechanical polishing (CMP) is then used to remove the excess copper and planarize the copper 20 with the top of the interlevel dielectric layer 12, as shown in FIG. 1E.
The copper CMP is a very critical step in a dual damascene process. Most Cu CMP slurries are aluminum based. Aluminum based slurries are very hard to remove. The Cu CMP process leaves residue, slurry particles, metal contamination and Cu-by products on the surface of the metal lines and IMD/ILD surface. Prior art post copper CMP clean processes use a scrubber that contacts each wafer in a single wafer process environment. Due to the single wafer process, the prior art has low throughput. The scrubber process also utilizes consumables, such as brushes. Furthermore, Cu is a soft metal that is very easily scratched. Accordingly, a non-contact, lower cost/high throughput post CMP clean-up process is needed.
The invention is a non-contact post CMP clean-up process. A corrosion inhibitor is used to protect the copper surface to prevent an electrochemical reaction between the p-well and n-well areas while polishing. A multi-step wet chemistry is used to clean all exposed surfaces without etching more than 100 xc3x85 of the copper, liner, or dielectric. The wet clean chemistry is a batch process that allows high throughput and is cost effective.
An advantage of the invention is providing a non-contact, high throughput, cost effective post-copper CMP clean-up process.
This and other advantages will be apparent to those of ordinary skill in the art having reference to the specification in conjunction with the drawings.